Fall detection is very important and has widely applications in older care, patient care, child care, disable care as well as safety for outdoor sports event. To develop a reliable fall detection system has huge market potential and great society impact. Conventional fall detection system is designed to detect whether a real fall event happens by matching falling acceleration data with pre-set models or thresholds using enormous different kinds of algorithm. However, a random fall event depends on actual situation and prior falling movement of the host. It is too complicated to have a precise model to mimic the real event. Despite of great efforts, there is no a successful product existing on the market with great impact. The present invention resolves this dilemma by directly measuring/sensing the relative position/orientation between the host body and direction of gravity at the spot where a falling event happens.
Related to fall detection, measuring the tilt angle respect to local gravity is also very useful. Currently, tilting angle is also indirectly measured with reference to local gravity or ground mostly through measuring acceleration via an accelerometer or gyroscope.
Detecting vibration with great sensitivity also has many applications. Conventionally, vibration detection is carried out by accelerometer (e.g. piezoelectric sensor or capacitive sensor), velocity sensor (e.g. electromagnetic linear velocity transducer), proximity probes (e.g. capacitance or eddy current), or laser displacement sensor. In this invention, a brand new sensor is proposed, which can be used to fulfill the requirements for the above mentioned tilt sensor or vibration sensor applications. Several embodiments of the designs with respective sensitivity are proposed.